1. Field of the Invention
The present invention relates to an oxide series superconductive sintered body, particularly an oxide series superconductive sintered body to be joined to a metallic member, and a method of producing the same.
2. Related Art Statement
Recently, in order to improve the mechanical strength of oxide series superconductors, oxide series superconductors have been earnestly desired to be used as joined bodies with metallic members.
Heretofore, as methods of joining an oxide series semiconductor and a metallic member, there are known (1) a method of plasma thermal spraying of an oxide series superconductor powder on a metallic plate, and heat treating the same at a temperature of 500.degree. C. or higher; (2) a method of applying a solution of elements constituting a superconductor on a metallic plate, and sintering the same at a temperature of 800.degree. C. or higher; and (3) a method of filling a superconductive oxide powder in a metallic tube, and sintering the same at a temperature of 800.degree. C. or higher.
The above methods can obtain joined bodies of a metallic member and a superconductive oxide of yttrium-barium-copper oxide, rare earth-barium-copper oxide wherein a portion or the whole of yttrium is substituted by other rare earth elements (except for Sc, Tb), bismuth-calcium-strontium-copper oxide with optional lead oxide, or thallim-barium-calcium-copper oxide. However, all the methods have drawbacks of necessitating high temperatures for the sintering or the heat treatment in obtaining the joined body of the superconductive oxide and the metallic member.
If a metal, such as aluminum, or copper, etc., is used as the metallic member for producing the joined body, various problems occur in that a superconductive oxide is reacted with the metallic member at such high treating or sintering temperatures to deteriorate its superconductive property, and the metallic member is oxidized by an oxidative atmosphere. If silver or a like metal that does not react with a superconductive oxide is used as the metallic member to be joined with the superconductive oxide, the cost is considerably increased, though the above problems are prevented.
Even if silver is used as the metallic member to be joined with a superconductive oxide, there are drawbacks in that, if the temperature of the joined body is decreased from a high temperature of 900.degree. C. or higher to room temperature, silver and the superconductive oxide are peeled from each other, or a crack occurs in the superconductive oxide, due to a difference in thermal expansion coefficients between the superconductive oxide and silver.
The above methods (1) of plasma thermal spray and (2) of application of a solution can not precisely control the composition of the sprayed superconductive oxide or densify the superconductive oxide, so that the superconductive property of the joined bodies are difficult to improve. While, the above method (3) of filling a superconductive oxide powder in a metallic tube has a drawback in that a superconductive oxide which necessitates a heat treatment for absorbing oxygen, such as yttrium-barium-copper oxide, is prevented from absorbing oxygen by the metallic tube.